The present invention relates to admixtures for making or modifying castable cementitious compositions, and more particularly to a basic-medium-soluble packaging system placed directly into a mixer wherein a castable cementitious composition acts to dissolve the packaging material.
Packaging for dispensing admixtures directly into concrete mixes is known. One benefit of such packaging is that admixtures to be contained in the packaging can be pre-weighed to reduce error at the application site.
Japanese Patent Application Sho 50-14722 (Laid Open Number) of Kiyoshi Watanabe et al. taught that a sack made of water-soluble film could be thrown into the hopper of a mix truck so as to introduce a surfactant into a mortar or concrete being mixed in the truck. Upon agitation of the mix, the sack began to dissolve in the water of the mix, and the contents could be dispersed therein. The water-soluble sack consisted of a water-soluble material such as polyvinyl alcohol, polyethylene oxide, amylose, methylcellulose, hydroxypropylcellulose, or starch.
U.S. Pat. No. 4,961,790 of Smith et al. disclosed a water-soluble container made of polyvinyl alcohol or polyethylene oxide and containing a solid admixture, e.g., water-reducing admixture, superplasticizer, fibers, or other agents for modifying concrete. Similar to Watanabe""s soluble sack, the bags of Smith et al. required an outer protective wrapper to prevent the bag from dissolving during transportation or before use at the construction site.
U.S. Pat. Nos. 5,203,629 and 5,224,774 of Valle et al. disclosed non-soluble bags, on the other hand, for introducing solid admixtures into a fresh concrete or mortar. Upon agitation in a mix, the paper (e.g., kraft pulp) disintegrated and allowed the admixtures contained inside the bag to be distributed within the concrete or mortar. With sufficient mechanical agitation of the concrete mix, the non-soluble bag material was broken down by the grinding action of the aggregates in the mix into harmless pulp. Although the non-soluble bags could be transported in outer packaging to facilitate palletizing, these bags were not prone to being destroyed simply by rain at the construction site, unlike previous bags that were made of water-soluble materials.
U.S. Pat. No. 5,224,595 of Sugimoto et al. pertained to an alkali hydrolyzable packaging material made of pulp fibers (e.g., made of wood, non-wood, rayon, polyester, hemp, etc.) bound together by a polymer. The polymer included polysaccharide derivatives such as carboxymethyl cellulose, carboxyethyl vellulose, and carboxymethylated starch, or their salts, as well as synthetic polymer binders (e.g., polymers of unsaturated carboxylic acids) and natural polymer binders (e.g., alginic acid, xanthum gum, etc.). The polymeric binder was weakened in the alkali environment of a fresh concrete mix, such that the fibrous bag material could fall apart and the package could release its contents into the mix.
U.S. Pat. No. 5,320,851 of de Mars et al. disclosed that semi-fluid or fluid cement admixtures could be encapsulated in a gelatin or wax that either ruptured, shattered, or disintegrated in the wet concrete during a period of mechanical mixing.
For non-soluble materials, such as the pulp component disclosed in Sugimoto et al. and Valle et al., and such as the wax component disclosed in de Mars et al., the mechanical agitation of the concrete mix must be sufficiently pursued to ensure that the packaging is sufficiently disintegrated within the cementitious mix.
The present inventors believe that faster and more convenient and economical packaging systems are needed.
In surmounting disadvantages of prior art packaging, the present invention provides water-insoluble, basic-medium-soluble polymeric packaging for making and/or modifying castable cementitious compositions. The packaging can be used for introducing cementitious binder(s), admixture(s), or a plurality of fibers, or a combination thereof, as a discrete unit into a mixer.
An exemplary packaging system of the invention comprises: at least one substance operative for making or modifying a castable cementitious composition; and a packaging for containing the at least one substance, the packaging having an integral member comprising a non-water-soluble, basic-medium-soluble polymeric material operative to package said at least one substance, to permit the introduction of said at least one substance into a mixer as a discrete unit, and to dissolve in a castable cementitious composition made or modified by said substance introduced by said packaging into a mixer. Exemplary polymeric packaging materials are prepared from a monomer mixture comprising an ester and an acid, the ester monomer having the structural formula 
wherein R1 represents H, CH3, or C2H5; and R2 represents CH3, C2H5, C3H7, or C4H9; and the acid monomer having the structural formula 
wherein R3 represents H, CH3, or C2H5. The ratio of ester to acid, preferably, is 1:1 to 20:1, and, more preferably, in the range of 3:1 to 4:1.
The packaging material is preferably extruded, molded, cast, spray-coated, dip-coated or otherwise formed into a continuous article or surface of an integral article, such as a film or rigid wall (e.g., self-supporting sheets) constituting the entire package or a portion of the packaging; or the packaging is made using the aforementioned polymeric material in a liquid-applicable form, such as a continuous coating for substances to be dispensed into a mixer. Preferably, the packaging is made by extrusion of continuous film or sheet or other shapes. The word xe2x80x9ccontinuousxe2x80x9d is herein used in the sense that the packaging material is substantially without pulp fibers being embedded in, or constituting, the wall of the packaging material. The packaging, for example, can be formed into a bag (e.g., pillow or pouch shape), a box, a tube, an envelope, a satchel, or a perimeter wrapping; or injection molding or blow molding, for example, can be used to make capsules, bottles, can shapes (e.g., cylindrical), or other rigid shapes (e.g., self-supporting either when empty or when filled with the substances) for packaging the additives or admixtures. The packaging material is also thermoplastic in nature, and therefore can be heat-seamed to seal at edges and openings. The packaging material of the invention does not dissolve under normal effects of water, unlike the materials taught by Smith et al. (U.S. Pat. No. 4,961,790). Moreover, unlike Valle et al. (U.S. Pat. Nos. 5,203,629; 5,224,774) and Sugimoto et al. (U.S. Pat. No. 5,224,595), the present invention does not require non-soluble pulp to be incorporated into the packaging walls.
Furthermore, the basic-medium-soluble polymers of the invention provide packaging material in a continuous form (e.g., film, coating, sheet, self-supporting wall, blow molded or injection molded shape such as a can, cylinder, bottle, shell, etc.) which is relatively easier to manufacture and handle, and can be broken down and dispersed more quickly in a cementitious composition in contrast to pulp fiber bags or wax encapsulates which require time-consuming mechanical comminution under abrasive mixing in a concrete mixing truck.
One advantage of the present invention, therefore, is the ability of the basic-medium-soluble material to be used in mortar cements which lack coarse aggregates.
Another advantage of using the basic-medium-soluble polymer as a packaging material is that its thermoplastic properties can be modified or enhanced. For example, in addition to the ability to provide three-dimensional shapes (e.g., capsules, ball shapes, etc.), the packaging can be melt-shrunken under the effect of heat (e.g., xe2x80x9cshrink-wrapxe2x80x9d type applications) such that the package (to be dispensed directly unopened or otherwise unreleased into the cement composition) can be made having a relatively smaller content-volume-to-outer-surface area ratio to facilitate introduction of the contained (or bundled, e.g., tied, perimeter wrapped) substance into, and disintegration and distribution within, the cementitious composition that is being modified. Thus, for example, the packaging can be used to pack structural reinforcing fibers in a densely packed formation (to increase bulk shipment capacity) while presenting minimal outer surface area. This could not be achieved using paper-based materials, which would lose strength when exposed to moisture.
Another advantage of the present invention is that it allows for use of dry or fluid admixtures, or a combination of both (so long as the admixtures packaged do not generate a basic medium operative to dissolve the packaging prematurely or contain organic solvents that dissolve the packaging material).
Moreover, packaging of the present invention can assume the shape of a bag, box, tube, or other shape to contain a plurality of fibers (and/or cement and other substances, such as admixtures, in dry or liquid form). Thus, the packaging can contain fibers for reinforcing concrete (and/or for inhibiting plastic shrinkage of concrete) and also containing a wet or dry water reducer (e.g., superplasticizer) for offsetting any decrease in concrete workability due to the fibers, as well as other admixtures (e.g., pigments, air control agents such as air entrainers, water repellants, permeability reducing agents, etc.) for further modification of the cementitious composition.
In other exemplary embodiments of the invention, a plurality of additives and/or admixtures can be packaged together in pre-measured quantities, such as combinations of air controlling agents (e.g., air entraining admixtures, air detraining admixtures) with one or more of superplasticizers, shrinkage reduction admixtures, corrosion inhibitors, and other admixtures. Due to the improved disintegration/selective-dissolvability of the packaging materials of the invention, separate packaged admixtures or admixtures can be contained within larger basic-medium-soluble packaging (e.g., a plurality of packages within a package), and thus be sold, shipped, and employed as an integrated system, preferably comprising separate packets or containers of premeasured admixture materials. Pre-measured ingredients can help to reduce errors by the operator of the mixing truck or equipment at the site.
Thus, a further exemplary packaging of the invention comprises at least two different additive/admixture components within one or more basic-medium-soluble containers. For example, a plurality of fibers and an admixture (e.g., a superplasticizer) can be contained within the same package (e.g., bag, pouch, can, etc.) or within separate containers (e.g., a package of superplasticizer contained within a package of fibers. Another exemplary embodiment comprises an admixture in fluid form (e.g., a liquid superplasticizer) packaged separately with or within a cement or shotcrete mixture in dry form (e.g., dry powder) in a bag or other container shape.
Still further exemplary packaging systems and applications of the invention may comprise a complete system for making a cementitious composition, such as fireproofing composition or shotcrete, by containing premixed amounts of cementitious binder(s), aggregate(s), and other substances such as fibers, admixture(s), or mixture thereof. The packaging system is tossed directly into a mixer and torn or ruptured open by mechanical action of the mixer, whereby the contents can combine with water in the mixer to form a castable cementitious composition into which the packaging material dissolves. No packaging waste materials therefore hinder the construction operation.
The present invention thus can be said to provide methods for making and/or modifying castable cementitious compositions using the aforementioned packaging. Other advantages and features of the invention are disclosed in further detail herein.